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Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.

Groß A, Kremling M, Marr I, Kubinski DJ, Visser JH, Tuller HL, Moos R - Sensors (Basel) (2013)

Bottom Line: An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed.With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer.The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Energietechnik, Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. andrea.gross@uni-bayreuth.de

ABSTRACT
An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.

No MeSH data available.


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NOx concentration detection at 650 °C: (a) course of NOx concentration cNOx,in, (b) sensor response ΔRrel, (c) linear correlation between ΔRrel and cNOx,in.
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f6-sensors-13-04428: NOx concentration detection at 650 °C: (a) course of NOx concentration cNOx,in, (b) sensor response ΔRrel, (c) linear correlation between ΔRrel and cNOx,in.

Mentions: The effect of NOx on the resistivity of KMnO4/La-Al2O3 was studied at 650 °C to investigate this temperature as being suitable for regeneration. The sample was exposed to the NOx concentration profile shown in Figure 6(a) with up to 8 ppm NO and 75 ppm NO2. ΔRrel is calculated from the impedance at 1 MHz due to the increased conductivity. Again, the conductivity of KMnO4/La-Al2O3 increases in the presence of NOx. But, as shown in Figure 6(b), at 650 °C, the value for ΔRrel follows the course of cNOx,in (instead of ∫cNOx,in dt) being characteristic of a common concentration-detecting gas sensor response. Despite the corresponding concentration-related characteristic line in Figure 6(c), which gives a linear correlation, the low sensitivity of only 2.7%/100 ppm NO2 limits the application of KMnO4/La-Al2O3 as a NOx sensing material operated at 650 °C.


Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.

Groß A, Kremling M, Marr I, Kubinski DJ, Visser JH, Tuller HL, Moos R - Sensors (Basel) (2013)

NOx concentration detection at 650 °C: (a) course of NOx concentration cNOx,in, (b) sensor response ΔRrel, (c) linear correlation between ΔRrel and cNOx,in.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3673092&req=5

f6-sensors-13-04428: NOx concentration detection at 650 °C: (a) course of NOx concentration cNOx,in, (b) sensor response ΔRrel, (c) linear correlation between ΔRrel and cNOx,in.
Mentions: The effect of NOx on the resistivity of KMnO4/La-Al2O3 was studied at 650 °C to investigate this temperature as being suitable for regeneration. The sample was exposed to the NOx concentration profile shown in Figure 6(a) with up to 8 ppm NO and 75 ppm NO2. ΔRrel is calculated from the impedance at 1 MHz due to the increased conductivity. Again, the conductivity of KMnO4/La-Al2O3 increases in the presence of NOx. But, as shown in Figure 6(b), at 650 °C, the value for ΔRrel follows the course of cNOx,in (instead of ∫cNOx,in dt) being characteristic of a common concentration-detecting gas sensor response. Despite the corresponding concentration-related characteristic line in Figure 6(c), which gives a linear correlation, the low sensitivity of only 2.7%/100 ppm NO2 limits the application of KMnO4/La-Al2O3 as a NOx sensing material operated at 650 °C.

Bottom Line: An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed.With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer.The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Energietechnik, Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. andrea.gross@uni-bayreuth.de

ABSTRACT
An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.

No MeSH data available.


Related in: MedlinePlus